What's the difference between a wallaby and a kangaroo?

Wallaby teeth are built to grind up leaves, while kangaroo teeth are built to slice up stalks of grass.

Marcus Williams, HowStuffWorks

If the guys on "CSI" and "Law and Order" can use dental records to identify human individuals, why not extend the same logic to animals? That's exactly what scientists have done. To be absolutely sure which animal you're dealing with, you have to compare their molars. Since the two species eat their meals in different habitats, their teeth have evolved over the years to suit the specific vegetable matter they consume.

The wallaby lives in bushy forest areas where it dines on mostly leaves. Because the wallaby has to crush and grind up leaves in its mouth, it needs flat teeth. Unlike the kangaroo, it doesn't do much cutting, so its crowns are less pronounced. However, the wallaby does retain a single cutting tooth on the top of its mouth for any occasional cutting needs. It also keeps its premolars; the kangaroo sheds its premolars.

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The kangaroo, which lives in more open treeless areas, chomps on mostly grasses. Because the kangaroo has to slice up stalks of grass in its mouth, it needs teeth that can accomplish the task. The kangaroo's teeth are curved with cross-cutting ridges for cutting and shearing grass. Its molars have higher crowns than wallaby teeth.

Are you still wondering whether Rocko is a kangaroo or a wallaby? Next time you're watching "Rocko's Modern Life," peer inside his mouth and check out his molars. If his creators know their stuff, you should see flat teeth and a sharp cutting tooth; Rocko is a wallaby. You'll also notice he's noticeably smaller than his buddies on the show, another telltale sign that he's a member of the wallaby species.

To learn more about kangaroos and wallabies and some other intriguing animals, investigate the links on the following page.

From Petites to XXLs

The Macropodidae family, to which wallabies and kangaroos belong, contains more than 54 species [source: Myers]. The seven foot (2.1 meter) tall Eastern gray kangaroo can travel at speeds of up to 35 mph (56 kph) and cover 25 feet (8 meters) of grassland in a single jump [source: "Eastern Gray Kangaroo"]. The Brush-tailed rock wallaby, which only grows about 30 inches (76.2 centimeters) tall, shelters in caves [source: Fountain]. With this kind of diversity, there are bound to be some exceptions to the differences outlined in this article.